Class C Surface Water Operator License
Practice Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2025|2026 Q&A | Instant Download Pdf
1. Which treatment process is typically first in a surface water plant after
screening?
A. Disinfection
B. Filtration
C. Coagulation
D. Fluoridation
Coagulation is typically the first chemical process after screening,
used to destabilize suspended particles for removal.
2. What is the primary purpose of a rapid mix basin?
A. Quickly disperse coagulants
B. Provide sedimentation time
C. Remove pathogens
, D. Store treated water
Rapid mix basins ensure uniform dispersion of coagulants before floc
formation begins.
3. In surface water treatment, which stage comes immediately after
coagulation and flocculation?
A. Disinfection
B. Aeration
C. Fluoridation
D. Sedimentation
Sedimentation allows heavy floc particles to settle before filtration.
4. Which device measures the turbidity of water?
A. Flowmeter
B. Nephelometer
C. Chlorinator
D. Manometer
A nephelometer measures turbidity by detecting light scattered by
suspended particles.
5. What is the primary purpose of alum in water treatment?
A. Disinfection
B. pH adjustment
C. Coagulation
D. Filtration aid
, Alum is a common coagulant used to destabilize suspended solids in
water.
6. Which form of chlorine is most commonly used in large surface water
plants?
A. Chlorine gas
B. Sodium hypochlorite
C. Calcium hypochlorite
D. Chloramine
Chlorine gas is widely used due to its cost-effectiveness and ability to
provide strong disinfection.
7. Which process removes dissolved gases like hydrogen sulfide from
water?
A. Sedimentation
B. Filtration
C. Disinfection
D. Aeration
Aeration is effective for removing volatile gases and oxidizing certain
contaminants.
8. What is the ideal pH range for effective coagulation with alum?
A. 9–10
B. 5.5–7.5
C. 3–4
D. 7.5–9.0
, Alum works best in a slightly acidic to neutral pH range to maximize
floc formation.
9. Which federal law governs the quality of drinking water in the United
States?
A. Clean Air Act
B. Resource Conservation and Recovery Act
C. Safe Drinking Water Act
D. Clean Water Act
The Safe Drinking Water Act sets national standards for drinking
water quality and safety.
10. Breakpoint chlorination refers to:
A. Adding chlorine until chlorine demand is met and free chlorine is
present
B. Removing all chlorine after disinfection
C. Adding chlorine only for taste and odor control
D. Adding chlorine for residual only
Breakpoint chlorination ensures enough chlorine is added to satisfy
demand and leave a free residual for disinfection.
11. Which filtration media is most commonly used in rapid sand
filters?
A. Anthracite only
B. Gravel only
C. Garnet only
Practice Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2025|2026 Q&A | Instant Download Pdf
1. Which treatment process is typically first in a surface water plant after
screening?
A. Disinfection
B. Filtration
C. Coagulation
D. Fluoridation
Coagulation is typically the first chemical process after screening,
used to destabilize suspended particles for removal.
2. What is the primary purpose of a rapid mix basin?
A. Quickly disperse coagulants
B. Provide sedimentation time
C. Remove pathogens
, D. Store treated water
Rapid mix basins ensure uniform dispersion of coagulants before floc
formation begins.
3. In surface water treatment, which stage comes immediately after
coagulation and flocculation?
A. Disinfection
B. Aeration
C. Fluoridation
D. Sedimentation
Sedimentation allows heavy floc particles to settle before filtration.
4. Which device measures the turbidity of water?
A. Flowmeter
B. Nephelometer
C. Chlorinator
D. Manometer
A nephelometer measures turbidity by detecting light scattered by
suspended particles.
5. What is the primary purpose of alum in water treatment?
A. Disinfection
B. pH adjustment
C. Coagulation
D. Filtration aid
, Alum is a common coagulant used to destabilize suspended solids in
water.
6. Which form of chlorine is most commonly used in large surface water
plants?
A. Chlorine gas
B. Sodium hypochlorite
C. Calcium hypochlorite
D. Chloramine
Chlorine gas is widely used due to its cost-effectiveness and ability to
provide strong disinfection.
7. Which process removes dissolved gases like hydrogen sulfide from
water?
A. Sedimentation
B. Filtration
C. Disinfection
D. Aeration
Aeration is effective for removing volatile gases and oxidizing certain
contaminants.
8. What is the ideal pH range for effective coagulation with alum?
A. 9–10
B. 5.5–7.5
C. 3–4
D. 7.5–9.0
, Alum works best in a slightly acidic to neutral pH range to maximize
floc formation.
9. Which federal law governs the quality of drinking water in the United
States?
A. Clean Air Act
B. Resource Conservation and Recovery Act
C. Safe Drinking Water Act
D. Clean Water Act
The Safe Drinking Water Act sets national standards for drinking
water quality and safety.
10. Breakpoint chlorination refers to:
A. Adding chlorine until chlorine demand is met and free chlorine is
present
B. Removing all chlorine after disinfection
C. Adding chlorine only for taste and odor control
D. Adding chlorine for residual only
Breakpoint chlorination ensures enough chlorine is added to satisfy
demand and leave a free residual for disinfection.
11. Which filtration media is most commonly used in rapid sand
filters?
A. Anthracite only
B. Gravel only
C. Garnet only
